1. Technical Field of the Invention
The invention concerns an apparatus for cleaning liquid fluids, in particular for the cooling water running to a heat exchanger, having a portion of pipe of circular cross section as a housing, a screening body and a suction device, which can be moved about an axis, on the inflow side for regional suction removal and consequently for cleaning the screening body.
2. Background of the Invention
DE 36 40 638 describes cleaning apparatuses for screening bodies that are installed in feed lines of heat exchangers, cover the cross section of the feed line and remove deposits on the flow-accepting side of the screening body by suction via a rotatable nozzle. The sectional plane of the rotationally symmetrical screening body lies in a cross-sectional plane of the feed line, for example in that of a flange connection. The nozzle of the suction-removal device is rotatable about the center axis of the portion of pipe or the feed line by an electric motor, the motor being arranged within the feed line on the flow-discharging side of the screening body. Access to the drive motor from the outside and similarly to bearings and seals is hindered in the case of this design. In addition to this, there is a relatively high space requirement, caused by the overall height of the cleaning apparatus.
U.S. Pat. No. 2,275,958 discloses an apparatus in which the actual filtering takes place in a housing which is generally cast and is mounted such that it is accessible via a cover in order to obtain an adequate screening area in the case of rotating suction devices. The axis of rotation is enclosed by a cylindrical screening body and lies perpendicular to the pipe axis of the feed line in a complex housing of its own, in which a fluid passes through the screening body from inside to outside. The motor lies outside the supply lines and can therefore be accessible from outside, as can seals or bearings. On account of the special design and overall size in relation to the nominal width of the feed line of the housing, the production of this known apparatus involves high expenditure and, in particular with the large nominal widths often required today, is so expensive that it cannot be used for filtering water at great flow rates.
The same also applies to the cleaning apparatus known from U.S. Pat. No. 1,977,601, which is designed as a valve. Screening bodies which correspond in cross section to a quarter circle, a half circle or virtually a full circle, with their opening facing the inflow side of the water, are proposed. The screening areas are also cleaned by a suction device. However, instead of a portion of pipe, complicated housings which can only be produced by casting are used, and the housings interact inseparably with the screening body and the suction device. Furthermore, it is required to form in the housing specially shaped pockets, which are intended to receive the dirt particles transported into the pockets from the screening area by the rotor.
DE 39 17 520 discloses a cleaning apparatus of which the screening body and suction device are fitted transversely in a pipe housing. However, as represented in FIGS. 1 and 2, the screening body is preferably made up of a plurality of different segments in order to come as close as possible to the circular shape of the cross section of the portion of pipe.
It is the object of the invention to improve an apparatus of the type stated at the beginning in such a way that further freedom of design for shaping the apparatus is provided in a simple way, the advantages of the known apparatuses being essentially retained.
To achieve this object, the invention proposes a cleaning apparatus having the features according to claim 1, which is hereby made to constitute part of the description.
The invention consequently dispenses with a complicated housing. Instead, a simple portion of pipe, in other words a piece of pipe of circular cross section, becomes an integral part of the apparatus as a filter housing. The invention uses in particular a screening body that is preferably bent from a metal screening plate, the cross section of which is designed as a U shape which is open toward the inflow side and has a bending radius that is constant in the bent region, or as part of this U shape.
According to the invention, the screening body consequently extends transversely in the portion of pipe, the regions which lie between the screening body and the inner wall of the circular portion of pipe being closed in a suitable way, for example by plates. For the invention it is important that the cross-sectional shape of the screening body is always oriented along the stated U contour. This means that the cross section is, for example, of a U-shaped design, with leg parts running parallel to one another and to the pipe wall, following on from the bent portions of the legs, or that the cross-sectional shape makes use only of part of the U contour, so that a relatively flat screening body is obtained. Of decisive significance in any case is that the cross section has a constant bending radius in the bent region, primarily for the interaction between the screening area and the suction device, but also for the desired filtering action and for the intrinsic stability of the screening area. The invention consequently allowsxe2x80x94depending on circumstances and needxe2x80x94virtually any desired choice of a cross-sectionally full or partial U shape as a screening area.
If a U shape with relatively long straight legs, extending parallel to the wall of the portion of pipe, beyond the bent region is chosen, the overall filtering area available is increased in size, even if the filtering area added in the region of the straight-extending legs cannot be cleaned with a suction device that can be swiveled about an axis. However, this has the effect of adding filtering areas which in emergencies serve as auxiliary screening areas for the passage of water, that is to say if there is imminent blockage of the screening area holding back the dirt particles. During normal filter operation, water only flows to a slight extentxe2x80x94if at allxe2x80x94through the auxiliary screening areas. With increasing soiling and imminent blockage of the screening area that is covered by the suction device and is normally cleaned, however, the cooling water flows increasingly through these auxiliary screening areas. As a result, for example, valuable time can be gained, in which the screening areas covered by the suction device can be cleaned after all, in order to prevent enforced shutdown. After all, definitive blockage of the screening area would bring the water flow to a standstill and have the consequence of an immediate enforced shutdown of the entire installation, for example an entire power plant block, for safety reasons.
The U shape, according to the invention, of the cross section of the screening body also ensures in particular that the cooling-water flow is not adversely affected by the straight legs of the U shape, extending parallel to the inner wall of the portion of pipe, and for example that vortexing at the inlet opening of the screening body is avoided. Rather, the water entering the screening body can flow along the straight and level running screening areas of the U shape of the screening body without vortexing until it meets the screening area in the bent region of the U shape. An increase in the size of the screening area brought about by using a screening body forming virtually a full circle in cross section, according to U.S. Pat. No. 1,977,601, or else a smaller increase in size in this way would always have the consequence of a very undesired vortexing of the water flow, on account of the constriction occurring in the inlet cross section of the screening body with subsequent widening, and the said vortexing may well reach into the bent region of the U shape of the screening body and reduce or even prevent the passage of water and the filtering action of wide regions of the screening body.
If, by contrast with the abovementioned relatively high U shape, only part of the bent region of the U-shaped screening area cross section is chosen as the screening area, a different objective is achieved, that is a cost saving, which however presupposes that the existing screening area is adequate. The swiveling angle, and consequently also the time taken for suction removal by the suction device for cleaning the filter areas, can in this case be shortened. The choice of a relatively flat U shape of the screening body cross section is significant in particular for greater nominal widths of the portion of pipe, since in this case a considerable reduction in the time taken for suction removal, and consequently a significant reduction in the cooling water removed by the suction device, can be achieved, so that more cooling water that flows through the pipe cross section is available for the heat exchanger generally connected downstream. In addition, in particular in closed cooling circuits, the devices connected to the suction device for receiving the amounts of dirt and water removed by the suction device can be made much smaller, saving space, in other words with lower costs in production and maintenance. The required screening area size for this embodiment is based on the maximum permissible pressure losses permitted in the respective case.
Using the U-shaped contour also allows, however, any desired intermediate solution between a relatively high and a relatively flat portion of the U shape of the screening body cross section to be used in practice, for example even a screening body of which the ends of the legs coincide with the end of the bent region. In this way, the suction device can cover, and clean, the entire screening area. There is no need for additional auxiliary filtering areas. In this case, it is also possible for the range of movement or swiveling of the suction device to clean only part of the screening area, so that in this case uncleaned auxiliary screening areas are also available. By making control system settings, furthermore, combined operating modes of the suction device can be chosen, for example occasional partial cleaning of the screening area that can be covered by the suction device, by which the cooling-water losses caused by the suction device can be reduced, can be coupled with complete cleaning at other times of the screening area that can be covered.
The invention is essentially based on the fact that generally the dirt is deposited on a screening area primarily in the central regions of the screening area, lying transverse to the flow of water, with the result that these regions also have to be cleaned the most frequently. With the aid of a cross-sectionally U-shaped screening area, an appropriate setting can be found for virtually all applications, on the one hand optimizing investment and operating costs and on the other hand providing safety reserves.
The abovementioned possibilities are considered in subclaims 2-5. Subclaim 6 is directed at configurations of the screening body which are provided with webs or ribs on their inner side, that is on their side facing the suction device. Although this design is known in principle from DE 39 17 520 as well, it can also be used advantageously within the scope of the invention. The development provided by the invention according to claim 7 provides that the height of the webs preferably protruding radially from the inner side of the screening area decreases from the center of the bent region of the screening body toward both side areas in such a way that the free edges of the webs lie in cross section on a circle, the center point of which lies outside the bent region and coincides with the pivoting axis of the suction device. This makes it possible for the height of the webs at the ends of the bent region to be close to or equal to zero and for relatively high webs to be obtained at the center of the bent region, where most dirt particles are deposited.
Subclaims 8 and 9 are directed at an advantageous way of increasing the inside diameter of the pipe housing, which is explained in more detail below. Subclaims 10, 11 and 12 concern an advantageous arrangement, shaping and operating mode of the suction device.
The development of the apparatus according to claim 13 serves to provide a bypass for emergencies, if blockage of the apparatus is imminent or has already occurred. The provision of additional screening areas at the end faces of the screening body is envisaged according to subclaim 14.
Since the achievable screening area is restricted by the constraints dictated by the U shape of the cross section of the screening body, it is expedient in certain cases to choose the inside diameter of the pipe housing to be greater than the clear diameter of the adjoining pipelines. This takes place in a particularly simple way by the pipe housing being provided with inner flanges, which are combined with outer flanges present on customary sections of pipe. In this way, an increase in diameter of up to 20% is achieved in comparison with the inside diameter of the adjoining pipes.
A particular advantage of the apparatus according to the invention is that it is extremely short, that is it can be accommodated in extremely restricted spaces by variable use of the basic cross-sectional shape of the screening body, corresponding to a xe2x80x9cUxe2x80x9d. The actual space requirement is determined by the size of the lateral lead-throughs for the suction-removal pipe or the shaft for the suction device, including a certain distance from the connection flanges.